NEW YORK (AP) - The former US congressman who stepped down in a scandal involving a tweeted photo of a bulging, underwear-clad groin now wants to become the next mayor of New York City.

Mr Anthony Weiner's audacious comeback quest seeks to transform him into the leader of America's biggest city.

"I made some big mistakes, and I know I let a lot of people down, but I also learned some tough lessons," he said in a video posted online.

Mr Weiner formally announced his plans Tuesday.

When the scandal broke in 2011, Mr Weiner initially claimed his Twitter account had been hacked. After more photos emerged - including one of him bare-chested in his congressional office - the married congressman eventually owned up to exchanging racy messages with several women, saying he'd never met any of them. He soon resigned.

He has said he wanted to keep the truth from his then-pregnant wife, Ms Huma Abedin, a longtime aide to former Secretary of State Hillary Clinton. Ms Abedin told The New York Times Magazine recently that she has forgiven him.

Mr Weiner's announcement follows another high-profile story of rapid political redemption: former South Carolina Gov. Mark Sanford, whose extramarital affair with an Argentine mistress derailed his political career in 2009, was elected to Congress last week.

According to a recent poll, nearly half of New York City voters said Mr Weiner shouldn't even run.

Still, no one is counting him out in the most competitive mayoral race in more than a decade.

The latest survey, a Quinnipiac University poll released on Wednesday, showed Mr Weiner getting 15 per cent of the Democratic primary vote, behind City Council Speaker Christine Quinn at 25 per cent. The poll which surveyed 1,082 voters and has a margin of error of plus or minus 3 percentage points.